Just spotted that while on its stand and spinning the back wheel the cassette has a low frequency wobble of about 1/2 mm on the largest cog.
Any idea what is going wrong? How I fix it?

Doesn't sound like a bent cassette unless its only one cog?

If 1 cog – rebend it back with a spanner/adjustable spanner

If its the whole casssette wobbling sounds like a bent axle?

What hub – Not Shimano by chance?

Shimano greening have a tendency to wobble anyway if you grab the cassette while stationary dies it move then too or just whilerotating?

XT hub, cassette moves if grabbed and pulled about – so i guess its somehow worked loose? can I tighten it via the lockring to sort this?

just crank up the cassette lockring to the required torque setting, or if you're a real man, tighten it up two clicks less than the tightest you can get it

Cheers, I try re-torqueing it tomorrow

I had this and my freehub bearings were shot.

DON'T just crank it as tight as you can, they can be difficult to remove later. Cassettes do not need to be gorilla'd on.

two thoughts: 1) freewheels often wobble like that. 2) any possibility of a bent/broken axle?

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joolsburger – Member

I had this and my freehub bearings were shot.
Posted 14 minutes ago # Report-Post

I had this.

Can you see if the freehub body is moving with the cassette or if the cassette is moving independently from the freehub body.

This will let you know if its the cassette of the freehub thats knackered?

Is a freehub wobbling like this necessarily a bad thing? Obviously not good, but it does not seem to be causing any issues and everything works OK.
No plans to gorilla anything, I'm torque wrench all the way 🙂

Mine has a 1-2mm wobble and has been like that since new

There's another topic, very similar to this, which is also live on the first page – might be woth a look.

It's not an SRAM one is it?

I bent mine when I stood up out of the saddle 😳

They've removed to much metal……